Numerous data suggest that the mesocorticolimbic dopamine (DA) system is critically involved in the organization and regulation of goal-directed behaviours of various types as well as in the mediation of the psychogenic effects of cocaine. To test the hypothesis that cocaine not only alters levels of extracellular DA within the mesolimbic DA system, but in addition changes the response of this system to reinforcing environmental stimuli, a study using high-speed chronoamperometry was done to evaluate the effects of cocaine (15 mg/kg, i.p.) on extracellular DA in the nucleus accumbens and to assess the effects of cocaine on the response evoked by the presentation of tail-pinch and palatable food. Cocaine was found to induce long-term biphasic changes in extracellular DA (an increase followed by a decrease) and, more importantly, to enhance DA increases evoked by both tail-pinch and food. The powerful enhancing action of cocaine on DA release, triggered by significant environmental stimuli and associated with behaviours of different types, is considered to be a possible primary mechanism of its rewarding or euphorigenic effect.